An epidemiological study on hyponatremia in psychiatric patients in mental hospitals in Nara Prefecture.

Hyponatremia occurs often in mental illness. The frequency was not noticed because of the uncharacteristic symptoms of mild hyponatremia. Of the 1,114 psychiatric inpatients retrospectively surveyed, 10.5% had hyponatremia. Not only patients with schizophrenia, but also patients with other mental illness, especially with epilepsy, having hyponatremia were confirmed. An early onset, a long duration of psychiatric disorder and a prolonged admission were statistically significant factors. Nicotine abuse was not a significant factor. It was suggested that the pathogenesis of hyponatremia in psychiatric patients might be involved in a chronic course of psychiatric disorders and poor response to psychopharmacotherapy.